The invention is directed to an apparatus for the inward and outward transfer of a workpiece in a vacuum chamber in which a conveyor means for conveying the workpiece is situated.
The coating of substrates, for example of compact disks (CD), is known in vacuum process technology, particularly in thin-film technology. Compact disks are a modern storage medium for digital information. The pressed plastic disks are coated in a sputtering process with, for example, an aluminum layer that is less than one ten-thousandth of a millimeter thick. The sputter-coating systems utilized for this purpose often have a rotary table for conveying the substrates.
A robot loads and unloads the system via a lock in a clean room. Proceeding from the lock, the rotary table conveys the substrate carrier together with the substrate through the vacuum chamber. The sputtering occurs with a high-performance sputtering cathode that is constructed as a magnetron.
German published application 3716498, incorporated herein by reference, has already disclosed an apparatus for the inward and outward transfer of an essentially flat workpiece in an evacuated chamber, and for supplying the workpiece into and returning the workpiece out of the region of a coating source for the purpose of treating the workpiece surface.
The apparatus of this published application is characterized by a coating mechanism arranged in the region of the coating chamber which has one or more cover-shaped workpiece carriers with the assistance of which workpieces can be brought into a position adjacent to an opening of the coating chamber. The opening can be closed, on the one hand, by the workpiece carrier and, on the other hand, by a lifter plate that is held and guided on a rotary table that is rotatably seated inside the coating chamber. The workpiece carrier can be pressed against the opening in the cover of the coating chamber by a lifting cylinder that is supported against the coating mechanism, and the lifting plate can be pressed by a lifting mechanism secured to the bottom plate.
Also of interest is U.S. Pat. No. 3,915,117, incorporated herein by reference. The abstract of this patent discloses a coating system for coating various products. A housing is provided which is formed of a fixed part and of a rotating covered part. The two parts together form a closed, gas-tight housing chamber. The housing chamber can be evacuated. A plurality of product carriers are carried on the movable part of the housing. The product holders are arranged at a distance from one another. They are movable so that they can be brought into various operation stations. One of these operation stages preferably comprises a gas-tight coating chamber. This chamber can be connected to the gas-tight housing chamber. The operation station is provided with separate means for evacuating the coating chamber. Movable seal means are provided at at least one station. The seal means serves the purpose of sealing the coating chamber and of the separation thereof from the housing chamber. A charging chamber is preferably attached in a separate station in the same way. It can be separately connected to the housing chamber. Alternatively, it can be separated from the housing chamber and can be separately evacuated.
European patent application 0291690, incorporated herein by reference, has disclosed an apparatus for the inward and outward transfer of an essentially flat workpiece in an evacuated coating chamber and for supplying the workpiece into and returning the workpiece out of the region of a coating source for the purpose of treating the workpiece surface.
The subject matter of this European patent application is characterized by a coating mechanism arranged in the region of the coating chamber and which has one or more cover-shaped workpiece carriers with the assistance of which the workpieces can be brought into a position adjacent to an opening of the coating chamber from which the opening can be closed, on the one hand, by the workpiece carrier and, on the other hand, by a lifting plate that is held and guided on a rotary dish that is rotatably seated inside the coating chamber. The workpiece carrier can be pressed against the opening in the cover of the coating chamber by a lifting cylinder that is supported at the charging mechanism, and the lifting plate can be pressed by a lifting mechanism secured to the bottom plate.
The apparatus of the prior art have the following disadvantages in practice, described hereafter.
The overall rotary table must be executed in extremely sturdy fashion. In order to avoid--sags in this respect, see the commentary on the bending stress of the substrate carrier that is provided later--, a sturdy construction of the substrate carrier is also necessary.
Great masses must therefore be conveyed during the process cycles. Due to the high mass moments of inertia that thus arise, the process cycles are executed in correspondingly slow fashion. A more economical and rational operation therefore has limits placed on it, given the systems of the prior art.
The substrate holder, given the apparatus of the prior art, must be constructed extremely sturdy because the substrate holder itself is exposed to high bending stresses when raising the lifting mechanisms for the substrate holder and when supporting the substrate holder against parts of the vacuum chamber.
In addition to the sturdy construction of the rotary table and substrate holder, the expense for individual parts is also extremely high in systems of the prior art. This expense is multiplied by a plurality of substrate holders in the rotary table.